Manufacture of alloys



Feb. z8, 195@ J, H, RAMAGE 2,498,769

MANUFACTURE OF ALLOYS Filed Oct. 2l, 1944 INVENTOR .I H. EAW/965 ATTORNEY patented Fell). 28, 1950 MANUFACTURE iii-,ALLOYSL John H. Ramage, Bloomfield? N'.v J'z, assignorv tu Westinghouse Electric Corporation, East-Pittsburgh, Pa., a` eorporationrofi Pennsylvania:

Application october `21, 1944, serial y10,559,693V 4 This invention relates to readily oxidizable refractory metal such as molybdenum, tungsten, and mixtures thereof, alloyed with metal such as chromium, to protect the same against oxidation'- when heated.

The principal object of my invention, generally considered, is to-provide alloys of molybdenum;

and/or tungsten, containing sumcient chromium, whereby the readily oxidizable refractory metal'is protected when used at elevated temperatures in' air or oxygen-containing atmospheres.

Another object of my invention is to providev chromium molybdenum, chromium tungsten, and tertiary alloys, in which the chromium content, although relatively small, is suficiently'high to protect the molybdenum and tungsten from oxidation at reasonably elevated temperatures, even though not enough to reduce the molybdenum or tungsten melting point, measured in degrees C., more than a few percent.

A further object of my invention is to produce an alloy of molybdenum and chromium, by taking an oxide of molybdenum, such as the sesquioxide or dioxide, M0203 or M002, wet it with a' solution of a salt of chromium, such'l as the acetate, nitrate or chloride, to the" proper proportions of chromium, dry, and reduce' in hydrogen.

A still further object of my invention is to produce alloys of metals such as molybdenum and tungsten with metal, such as chromium, to protect against oxidation at elevated` temperatures, comprising impregnating an oxide of molybdenum, such as the dioxide, or the corresponding oxide of tungsten, with'a solution of al salt of chromium, drying with constant stirring to avoid segregation of the liquid, reducing in hydrogen at a relatively low temperature to get molybdenumv or tungsten powder and well-distributed chromium oxide, press, treat the article so-pro duced in wet hydrogen to a well-sintered mass at relatively high temperatures, and nally treat the sintered article in dry hydrogen to hasten and complete the reduction of chromium and its alloying with the other metal.

Other objects and advantages of the invention will become apparent as the description proceeds.

Referring tothe drawing:

Fig. 1 is a vertical sectional view of a receptacle for mixing the selected oxide of molybdenum with a solution of the selected salt of chromium.

Fig. 2 shows the apparatus of Fig. l during a subsequent stage in which the mixture is being dried, as by means of steam, while stirring.

Fig. 3 is a vertical longitudinal sectional view of an' electric reducing furnace in which the molyb- 4" Claims. (Cl. '75l-22) denumA oxide- 'constituent' fil 2' v Y 3 ofn tliej mixture-is re-I duced; w

Fig. 4 is'a'vertical'sectionalvview of a-hydraulie' press inA which'slugs ofthe mixture, reduced" in y the furnace ofFig; 3, are formed.

Fig; 5 isa vertical sectionalview'of asinterng furnace in which'thev slugs'producedin the press of'Fig; 4, are sintered. Fig. 6"is a vertical sectionalview ofthefurnacfe shown in Fig. 5duringa subsequent treatment in which the wet hydrogenJ is replaced by dry hyi drogen. f

I will now'describethe preparationof'a m'oly-b'` denum-chromiun'r alloy of proportions suchL that the melting point will b'e'ne'arA that ofthe molybdenum, that is, above 90%. orI the melt-ing point of molybdenum measured" indegreesC.,y for small percentages of chromiumfsay from about 1/2 to 2%, as' disclosed in thek Antonpatent,` No. 2,304,297, for example; It will,- however, be un'i derstood thatl a simular process is applicable t the manufacture of other molybdenuin-chromium alloys, as well asto the manufacture of alloys of tungsten and" chromium and tungsten, molybde= num andl chromium.

Referring to' the drawing in detail, thereis', shown in Fig. 1 a receptacle I l in whichis placed av desired mass of a' powdered oxide ofi molybdenum l2, such as the brown variety M602; Upon thismass isy poured asolution I3 of a salt of chromium, such as'th'e acetate', nitrateor chloride, which are equivalent forme-purpose, as they all are Asoluble and no'deleterious ma; terial remains after decomfposition(l The amount of solution applied depend'son the concentration and on the percentage* of? chromium desiredfin thev alloy. During the addition of the solution; the mass is constantly stirred, as' by meansofa rod hl, while the receptacleis heated, preferably by means ofsteam |5i On' accountV of drying with constant stirring,v segregation of the liquid is avoided and a mixture of molybdenum oxide uniformly impregnatedwith the selecte'd salt if chromium, is obtained.4 f

The dry powdered-impregnated oxide' I12`iis then placed in suitable receptacles or"boats ItV and y passed through areducing furnace lil, comprising a suitably insulated' tube. t8' ofv refractory mety terial, such. as alumina, surrounded by. af coilf-LS of molybdenum or tungsten through which.: elect'- tricity is passed to supply: the heating power.rv The atmosphere inthe furnace, for'reducing, thezpowe deraas welll as protectingthe heatingl coil, is pref-f erably dry hydrogen,l although other reducing at mospheresmay be used, if desired. The furnace CTI it is not necessary to use diluted hydrogen be- Y cause the starting oxide is the dioxide rather than molybdenum trioxide,n although any of the reducing atmospheres there suggested may be employed.

After the reduction has been effected, the powder is removed from the furnace and formed into slugs or other desired articles 2|, as in a die 22 by means of a plunger l23 operated by a hydraulic press 24, so that sufficient pressure is applied to allow for handling ofthe formed slugs.

As an alternative, especially where high percentages of chromium are used in making the alloy, it may be desirable to remove the powder from the reduction furnace and treat it in a sintering furnace, such as illustrated in Fig. 5 or Fig. 6, in a dry hydrogen atmosphere at temperatures between 1600 and 1680 C., in order to remove the bulk of the oxygen from the chromium oxide to avoid substantial shrinkage or the possible formation of voids in the slugs or articles subsequently pressed from the powder.

The pressed slugs or other articles 2| are, after removal from the die, placed in a sintering furnace 25 which may be the same or like the furnace Il, except that said slugs are there first treated in a wet hydrogen or other reducing atmosphere, like the molybdenum articles of the Hall et al. Patent No. 2,431,690, previously referred to, and owned by the assignee of the present application to temperatures between 1600 and 1680 C. until the slugs or other articles are well-sintered. This treatment produces sintered molybdenum with partly-reduced chromium oxide well-distributed therethrough.

The treatment is then continued at about the same temperature, that is, between 1600 and 1680 C., as illustrated in Fig. 6, with the substitution of dry hydrogen or other reducing atmosphere, for wet hydrogen or other reducing atmosphere, to thereby hasten the reduction of the chromium and its alloying with the molybdenum until the operation is completed. It will be understood that the same furnace 25 is preferably employed, merely the water content of the treating atmosphere eliminated so that it is dry.

Although it will be understood that chromium is not readily reduced by hydrogen when free, yet in the presence of another metal such as molybdenum which absorbs or alloys with the nascent chromium as it becomes reduced, such reduction is effected and the nal product is a well sintered alloy of molybdenum and chromium.

Although I have specifically disclosed the manufacture of an alloy of molybdenum and chromium, it will be understood that a similar process may be employed for manufacturing alloys of tungsten and chromium and molybdenum, tungsten and chromium, the only difference being that for tungsten alloys the sintering temperature is correspondingly raised to that usually employed for tungsten, from that usually employed for molybdenum, when tungsten is substituted for molybdenum.

Although preferred embodiments of my invention have been disclosed, it will be understood that modifications may be made within the spirit and scope of the appended claims.

I claim:

1. 'Ihe method of forming an alloy of a metal selected from the group consisting of molybdenum, tungsten and mixtures thereof, with such a proportion of chromium that its melting point will be above 90% of that of the selected metal as measured in degrees C., for protection against oxidation at elevated temperatures, comprising forming an intimate mixture of an oxide of the selected metal with a solution of a -salt of chromium in the amount to give the proportion referred to, drying the mixture and heating it in a reducing atmosphere at a relatively low temperature to produce the selected metal with an oxide of chromium well-distributed therethrough, pressing said mixture suiciently to allow for handling the formed articles, treating said formed articles in a wet reducing atmosphere at a temperature between 1600 and 1680 C. to produce a well-sintered mass of metal, with some reduced chromium, and finally treating the pressed mass in a dry reducing atmosphere at a temperature between 1600 and 1680 C. to hasten the complete reduction of chromium and its alloying with the selected metal.

2. The method of forming an alloy of a metal selected from the group consisting of molybdenum, tungsten and mixtures thereof, with such a proportion of chromium that its melting point will be above 90% of that of the selected metal as measured in degrees C., for protection against oxidation at elevated temperatures, compri-sing forming an intimate mixture of an oxide of the selected metal with a solution of a salt of chromium in the amount to give the proportion referred to, drying the mixture and heating it in hydrogen at a relatively low temperature to produce the selected metal with an oxide of chromium well-distributed therethrough, pressing said mixture suiciently to allow for handling the formed articles, treating said formed articles in wet hydrogen at a temperature between 1600 and 1680 C. to produce a well-sintered mass of metal with some reduced chromium, and finally treating the pressed mass in dry hydrogen at a temperature between 1600 and 1680 C. to hasten the complete reduction of chromium and its alloying with the selected metal.

3. The method of forming an alloy of molybdenum with such a proportion of chromium that its melting point will be above 90% of that of molybdenum as measured in degrees C., for protection against oxidation at elevated temperatures comprising forming an intimate mixture of molybdenum oxide with a solution of a salt of chromium, drying the mixture and heating it in hydrogen at a relatively low temperature to produce molybdenum with an oxide of chromium well-distributed therethrough, pressing said mixture suiciently to allow for handling the formed articles, treating said formed articles in wet hydrogen at a temperature between 1600 and l680 C. to produce a well-sintered mass of molybdenum, with some reduced chromium, and finally treating the pressed mass in dry hydrogen at a temperature between 1600 and 1680 C. to hasten the complete reduction of chromium and its alloying with the molybdenum.

4. The method of forming an alloy of molybdenum with such a proportion of chromium that its melting point will be above 90% of that of molybdenum as measured in degrees C., comprising 4forming an intimate mixture of molybdenum oxide with a solution of a sa1t of chromium in the amount to give the proportion referred to, drying said mixture and heating in dry hydrogen at a temperature between 1600 and 1680 C., in order to remove the bulk of the oxygen from the chromium oxide to avoid substantial shrinkage and the possible formation of voids, pressing said mixture sufficiently to allow for handling the pressed mass, treating said pressed mass in a Wet reducing atmosphere at a temperature between 1600 and 1680e C. until well sintered, and finally treating the pressed mass in a dry reducing atmosphere at between 1600 and 1680 C. to hasten the complete reduction of chromium and its a1- loying with molybdenum.

JOHN H. RAMAGE.

REFERENCES CITED The following references are of record in the le of this patent:

Number 15 Number UNITED STATES PATENTS Name Date Farkas Nov. 14, 1911 Weintraub May 12, 1914 Copland Oct. 23, 1923 Graai Mar. 6, 1928 MacFarland Apr. 14, 1931 Iredell et al. Sept. 24, 1940 Schlecht et al May 20, 1941 Anton Dec. 8, 1942 Rennie Apr. 9, 1946 Hall et al. Dec. 2, 1947 FOREIGN PATENTS Country Date France Dec. 24, 1931 

1. THE METHOD OF FORMING AN ALLOY OF A METAL SELECTED FROM THE GROUP CONSISTING OF MOLYBDENUM, TUNGSTEN AND MIXTURES THEREOF, WITH SUCH A PROPORTION OF CHROMIUM THAN ITS MELTING POINT WILL BE ABOVE 90% OF THAT OF THE SELECTED METAL AS MEASURED IN DEGREES C., FOR PROTECTION AGAINST OXIDATION AT ELEVATED TEMPERATURES, COMPRISING ONE OF THE SAID CAMS TO CAUSE THE SLASHING KNIFE TO BE OPERATED PERIODICALLY, THE RATIO BETWEEN THE 